This invention relates to safety devices. In particular, this invention relates to a method and apparatus for deploying and retracting vehicle safety devices such as stop signs and crossing gates.
Vehicles such as school buses serve to pick up and discharge passengers. When passengers are discharged from the front door of the bus to the side of a road, the passengers may attempt to cross the road immediately in front of the bus. This poses a safety risk, particularly with school-age children, as the road immediately in front of the bus may be in the bus driver""s blind spot, i.e. outside the bus driver""s range of vision. Accordingly, safety measures such as crossing gates mounted on the front of the bus have been employed for many years. An example is shown in U.S. Pat. No. 5,406,250 issued Apr. 11, 1995 to Reavell et al., which is incorporated herein by reference.
These crossing gates are typically hinged to the front of the bus at the side nearest the front door. In the retracted state, the crossing gate is held parallel to the front of the bus. When the bus stops and the front door is opened, the crossing gate is extended until it is substantially perpendicular to the front of the bus, effectively providing a barrier at the side of the road of typically at least one meter. Discharged passengers who wish to cross the road must walk around the crossing gate, causing them to pass through the driver""s range of vision. After the passengers have passed beyond the front of the bus, the crossing gate is retracted.
An example of a prior art retraction mechanism is U.S. Pat. No. 4,816,804 issued Mar. 28, 1989 to Reavell, which is incorporated herein by reference. The apparatus controlling the safety device, in the case of U.S. Pat. No. 4,816,804 a school bus stop sign, is automatically responsive to the opening and closing of the bus door such that when the door is opened, the apparatus swings the hinged sign to its extended position, and when the door is closed, the apparatus returns the sign to its retracted position. The apparatus comprises a unidirectional motor coupled to the hinged sign through an eccentric drive and a link arm. The link arm is provided with a preloaded, helical compression spring which absorbs the shock of mechanical leverage.
However, apparatus such as these do not prevent inadvertent deployment of the safety device. Although a compression spring in the link arm can help to prevent excessive forces from damaging the mechanical linkages on the safety device, it is not able to prevent unintended deployment of the safety device when the device is exposed to high winds. Wind may catch the safety device, especially in the case of a gate, and partially or fully deploy the gate or even damage the device. Particularly if the bus is in motion, such accidental deployment of the gate is a significant hazard. Even when the bus is parked, the gate is more susceptible to breakage and damage from high winds when extended inadvertently.
One solution to this problem has been to employ an electromagnetic device to hold a crossing gate in the retracted position. Such an electromagnetic device would be activated while the safety device is in the retracted position, and deactivated when the safety device is to be deployed. However, an electromagnetic device can only be employed while the bus is in operation, because the power required to energize the electromagnet is supplied by the vehicle electrical system. This is not a satisfactory solution for use when the bus is not in operation and the power is shut off and parked, for example where high winds or storms strike overnight. Furthermore, the electromagnetic device cannot detect when the gate does not fully retract (for example if an obstruction becomes trapped between the gate and the vehicle body), nor can it compensate for slight misalignment or deviations in the path of retraction.
It would accordingly be advantageous to provide a device for engaging a reciprocating arm such as a safety gate, such that in the retracted position the arm is positively engaged by mechanical means. It would further be advantageous to provide such a reciprocating arm with means for monitoring the position of the arm to detect when the arm is fully retracted and the locking mechanism is properly engaged.
The present invention provides an apparatus for operating a vehicle safety device comprising a reciprocating arm, which allows the reciprocating arm to be locked in the retracted position. The reciprocating arm is mounted to a drive motor, which extends and retracts the arm, connected to a drive circuit. The locking mechanism comprises a rotor provided with at least one retaining finger defining a hook for engaging the reciprocating arm. The rotor is rotatably mounted to a drive motor in the path of retraction of the arm, and connected to the drive circuit. When the reciprocating arm has reached the retracted position, the drive circuit rotates the rotor in a locking direction, until the retaining finger engages the reciprocating arm. When the reciprocating arm is to be moved to the deployed or extended position, the drive circuit activates the rotor drive in the unlocking direction until the rotor releases the reciprocating arm, and then activates the reciprocating arm drive to deploy the arm.
The invention further provides a means for monitoring the status of engagement of the rotor, so that if the reciprocating arm is not fully retracted when the rotor drive is activated to engage the reciprocating arm, the rotor will continue to rotate in the locking direction, and the reciprocating arm continues to retract, until the rotor drive engages the arm and the circuit senses that the rotor drive has stalled.
The present invention thus provides an apparatus for operating a safety device comprising an arm having extended and retracted positions, comprising: a drive motor for moving the arm between the extended and retracted positions; and a lock for engaging the arm in the retracted position, comprising a rotor mounted in a path of retraction of the arm, having a locked position and an unlocked position, and comprising at least one retaining finger for engaging the arm in the locked position; a drive motor for rotating the rotor between the locked and unlocked positions; and a drive circuit for operating the arm drive motor and the rotor drive motor, comprising a circuit for sensing stalling of the rotor drive motor and deactivating the drive circuit in response thereto.
The present invention further provides an apparatus for operating a safety device comprising an arm having extended and retracted positions, comprising: a drive motor for moving the arm between the extended and retracted positions; and a lock for engaging the arm in the retracted position, comprising a rotor mounted in a path of retraction of the arm, having a locked position and an unlocked position, and comprising a pair of opposed retaining fingers for engaging the arm in the locked position, the retaining fingers having hooked ends for engaging over edges of the arm in the locked position, a distance between the hooked ends being greater than a height of the arm; a drive motor for rotating the rotor between the locked and unlocked positions; and a drive circuit for operating the arm drive motor and the rotor drive motor; whereby when the rotor is rotated to the unlocked position the arm can be extended through an opening between the hooked ends of the retaining fingers.
In further aspects of the apparatus of the invention: each retaining finger comprises a hooked end adapted to engage the arm; the rotor comprises two retaining fingers disposed in opposition; the arm comprises bevelled upper and lower edges; when the apparatus is in the retracted position the drive circuit periodically activates the rotor drive motor in a locking direction; to extend the arm, the arm drive motor is activated after the rotor drive motor; a stop is provided in a path of rotation of the rotor, whereby the rotor cannot rotate beyond the stop in an unlocking direction; and/or the stop comprises a slanted edge whereby the rotor can rotate beyond the stop in a locking direction.
The present invention further provides a method of operating a safety device comprising an arm having extended and retracted positions, comprising the steps of: a. moving the arm from an extended position to a retracted position; b. rotating a rotor mounted in a path of retraction of the arm, the rotor having a locked position and an unlocked position and comprising at least one retaining finger for engaging the arm in the locked position; and c. sensing stalling of the rotor and deactivating the device in response thereto.
In further aspects of the method of the invention: the rotor comprises at least one retaining finger comprising a hooked end adapted to engage the arm and stall the rotor drive motor; the rotor comprises two retaining fingers disposed in opposition; and/or the method comprises the additional step of, when the apparatus is in the retracted position, periodically activating the rotor drive motor in a locking direction.